Study of nanomechanical properties and nanotribological behavior of BCN films deposited by magnetron sputtering

Boron carbon nitride (BCN) films were deposited by d. c. magnetron sputtering. The films with various content of N were obtained by varying N₂/Ar flow ratio in the mixed gas from 0.0 to 0.3. Structures and compositions of the films were investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The nano-hardness, elastic modulus and nanotribological behavior of films were studied by a nano-indenter. Continuous stiffness measurement and lateral force measurement were used to measure the hardness and scratch behavior respectively. The loads used in scratch test were 2, 5, 10 and 20 mN. The results show that the nitrogen content had a rising tendency and then came to the saturation stage with increasing N₂/Ar flow ratio. Nitrogen in the film was prior to binding with B for forming sp² B-N bond, and then with C for forming C = N bond when the N₂/Ar ratio was over a certain value. The increase of N₂/Ar flow ratio decreased the hardness and elastic modulus. The scratch depth of BCN films were mainly depended on the component of bonding structures in the films, but the effect of bonding structures on the friction coefficient was not obvious. The scratch depth of BCN films increased with the increasing of the nitrogen concentration. The scratch depth of the BCN film increased with the increasing of the loads. Coefficient of friction of the film was about 0.1 before fracture, but increased quickly to 0.46 after fracture.